Novel environmentally sustainable surface coatings for textiles

Halogen-based flame retardant back-coatings are commonly used for flame retarding UK furnishing fabrics. Their use, however, has become the focus of environmental attention because of claimed ecotoxicological properties of brominated flame retardants (BrFRs). In the specific case of textiles for domestic furnishing fabrics, BrFRs have significant usage and enable most fabrics to pass the flammability testing requirements with both cigarette and simulated match sources since 1988 in the UK. Such treatments achieve a pass after the mandatory 30 min, 40 °C water-soak durability test. Recent innovative developments such as those based on sol gel chemistry have focused on the enhancement of the char-forming efficiency to create heat barrier systems incorporated within silica networks. These are able to create a physical barrier on the textile surface, thus protecting the underlying textile structure. While several recent papers have demonstrated that it is possible to improve the flame retardancy of fabrics by sol-gel treatments by using silica precursor and flame retardants, none of these has been tested as a barrier fabric over flammable polyurethane foam and very few have acceptable levels of durability. The main aim of this PhD is to develop environmentally sustainable flame retardant textile coatings by using novel organic – inorganic hybrid formulations (e., sol-gel) and processing techniques. To achieve this, initially three different flame retardants, based on Sb-Br formulations and acrylic binding resin, for back-coating on 100% cotton and 100% polyester fabrics were studied to enable the creation of a “benchmarking” set of flammability results against which future novel treatments could be compared. The fire performance of these back-coated fabrics was evaluated by using a simulated match test (SMT) to replicate the BS 5852: 1979: Source 1 standard for furnishing fabrics, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and cone calorimetry, while the physical characteristics of the fabrics were studied by stiffness testing and colour difference measurement (using Grey Scales). In order to develop a novel semi-durable flame retardant for 100% cotton fabric, a modified sol-gel treatment technique has been studied. It was first established that the best way to apply the selected sol-gel method to 100% cotton fabric was to simultaneously add a salt-based flame retardant combination of diammonium phosphate and urea to the silica precursor, tetraethylorthosilicate, by using a conventional pad-dry technique, commonly used for textiles. Subsequently, polydimethylsiloxane (PDMS), which belongs to a group of polymeric organosilicon compounds, was introduced and added to the sol-gel formulation to improve the hydrophobicity of the overall treatment. Drying at 110 °C for 10 min and curing at 150 °C for 5 min gave the most water-soak-durable sample. This sample passed the SMT after water-soaking, which was the aim of this project. The fire performance of these sol-gel cotton fabrics was evaluated by using a horizontal burning test, the simulated match test (SMT), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and cone calorimetry, while the physical characteristics of the fabrics was studied by stiffness testing, tensile, flexural testing and colour difference measurement. The surface morphology of the samples was studied by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and the phosphorus content of samples before and after water-soak testing was analysed by using inductively coupled plasma spectrometry (ICP), acid digestion and ICP analysis of phosphorus and X-ray photoelectron spectroscopy (XPS). Using these techniques, the flame retardant mechanisms of the successfully developed sol gel, flame retardant treatments were evaluated and compared with those by which the conventional bromine-containing back-coatings function